This invention deals with the making of a "superior coke" in a closed, pressurized system for use in an iron making furnace such as a blast furnace, wherein iron ore, coke and stone are charged substantially in layers. The coke serves as a fuel and as a base to form a reducing gas in order to convert the iron ore to molten iron. The superior quality of the coke resides in providing coke that is uniform in moisture and uniform in stability. These two features being of major importance for rendering the blast furnace more efficient from the standpoint of productivity, lower coke consumption, and reduction in CO.sub.2 formation.
Conventionally, incandescent coke is pushed into a quench car which is moved to a quenching tower, and about 60,000 liters of water are showered onto 26 tons of coke in about 90 seconds in order to cool the coke; this manner of coke quenching results in non-uniform moisture content in the coke. Further in making coke in a space that contains the coal to be coked with indirect heat originating from walls, the coal next to the walls sees a higher temperature than the coal at the center of the space; this condition leads to a coke with a non-uniform stability, the stability of the coke being the strength of the coke which in today's industry standard is set at an index of 60.
Discussion
In having coke that is non-uniform in both moisture and stability, forces the operator of the blast furnace to charge extra coke in order to prevent the furnace from being sluggish. But since the cost of coke in 1997 dollars averaged $130/ton, a reduction in coke consumption of even 3% in a blast furnace of 2.5 million tons of iron capacity/year (with a coke consumption of 0.4 tons of coke/ton of iron), means a net saving in operating costs of $3.9 million in a single year.
In practice, coke of uniform moisture and of uniform high stability means "better coke", by virtue of having a fuel for the blast furnace whose thermal value is predictable, and whose strength resists early deterioration as it descends in the furnace towards the hearth. Therefore to lower operating costs and to minimize the formation of CO.sub.2, the reduction in the consumption of coke per ton of molten iron produced becomes paramount.
When making coke from coal by conduction from heat that originates from a hot wall, the coal first expands, and when fully devolatilized the coke contracts. The full contraction of the coke is a necessary requirement to obtain the highest and most uniform stability in the coke, in order to reach this goal of uniform and high stability, the coal must be heated to such a degree as to completely devolatilize the coal with thermal energy to cause all the partitions forming the pores in the coke to shrink to such an extent as to reach a stable limit. Therefore in making coke in an oven which consists of heating coal in a space of about 18 inches which is provided between two walls which are heated indirectly, the coal which is adjacent to the walls is heated to a higher temperature than the coal which is not contiguous to the hot walls. This condition makes the coke non-uniform in stability with the coke produced at the center of the space between the walls being the least stable. In view of the above factors the objectives of the invention are described below.
Objectives Of The Invention
The main object of the present invention is to provide an environmentally closed method that operates at pressure capable of producing coke of uniform moisture.
Another object of the present invention is to provide an environmentally closed method that operates at pressure capable of producing coke of uniform stability.
Still another object of the invention is to provide an environmentally closed method that operates at pressure capable of producing coke of uniform moisture as well as of uniform stability.
Yet another object of the present invention is to provide an environmentally closed method that operates at pressure capable of producing coke of a stability exceeding the standard of 60.
Therefore another object of the present invention is to produce a coke of superior quality in order to lower the operating costs of an iron making furnace by reducing the rate at which the coke is consumed while at the same time reducing the formation of CO.sub.2 when making iron.